Feed waste detector

Abstract

A method and a device for detecting fodder waste/loss within a fish enclosure (1), where a sound transmitter (4) and a hydrophone (6) are disposed as an upwardly directed echo sounder close to the bottom of the enclosure (1). Sound echoes from objects situated above the sound transmitter (4), are picked up by the hydrophone (6). A measuring unit (8) separates signals from the hydrophone (6) into various frequency bands close to the transmitted sound frequency. The distance and amount of the objects are determined in a way similar to the one used in echo sounders. Sinking objects will cause rejected sounds having frequencies slightly higher than the transmitted frequency, so called Doppler effect, and the frequency difference is a measure of the sinking speed of the object. An analyzing unit (10) emphasizes frequencies corresponding to a characteristic sinking speed for the actual type of fodder (2) and gives signals about fodder waste/loss when a predetermined minimum amount of objects having the characteristic sinking speed are detected within a predetermined distance area.

I claim: 
     
       1. A method for detecting fodder loss in fish enclosures immersed in water, wherein a sound transmitter and a sound receiver are positioned proximate the bottom of the enclosure and are upwardly directed, comprising the steps of: a) transmitting sound waves upwardly by said sound transmitter;   b) receiving downwardly reflected sound waves from objects, including fodder, in said enclosure by said sound receiver;   c) separating said reflected received sound waves into a plurality of frequency components;   d) analyzing said frequency components to determine whether the objects reflecting said sound wave frequency components are moving toward or away from said sound receiver; and   e) analyzing said frequency components to evaluate the rate of movement of objects toward said sound receiver, and thereby to identify and evaluate the amount of fodder loss through sinking in said enclosure.   
     
     
       2. The method of claim 1, wherein the steps of transmitting and receiving further comprise analysis of reflected sound wave frequencies originating from within a specified distance. 
     
     
       3. A combination of a fish enclosure immersed in water and apparatus for detecting fodder loss in the fish enclosure, said enclosure having a feeding area and a restricted area below said feeding area, the apparatus comprising: a) a sound transmitter positioned beneath said restricted area of said enclosure and adapted for transmitting sound waves at a predetermined frequency toward said restricted area, whereby fodder particles falling in said restricted area at a characteristic speed reflect said sound waves toward the sound transmitter at a characteristic frequency;   b) a sound receiver proximate the sound transmitter and configured for receiving said sound waves directed by said sound transmitter and reflected from said fodder particles; and   c) an analyzer in electronic communication with said sound receiver, said analyzer configured to detect sound waves having the characteristic frequency and to generate an output signal related to the intensity of the sound waves having the characteristic frequency, whereby the fodder loss can be determined.